1. Field of the Invention
The present invention relates to an image forming apparatus configured to transfer a toner film formed on a transfer and fixing belt to a recording medium.
2. Description of the Related Art
A simultaneous transfer and fixing type image forming apparatus is being put into practical use lately. The image forming apparatus is configured to transfer a toner image formed on an image carrier to an intermediate transfer belt and to fix the toner image on the intermediate transfer belt to a recording medium by overlapping and by heating and pressing them together as disclosed in Japanese Patent Application Laid-open No. 2001-272866 for example. However, because the simultaneous transfer and fixing type image forming apparatus has a possibility of causing unevenness of density on an image due to melt toner that flows into concavities on a surface of the recording medium, there is proposed a toner film transfer type image forming apparatus configured to form a toner film and to transfer this toner film to a recording medium.
Specifically, Japanese Patent Application Laid-open No. 2005-266304 discloses a method including processes of forming a toner film by heating and pressing a toner image carried on a transfer and fixing belt, overlapping a recording medium with the toner film in which a melt layer has been formed by heating a surface thereof, and pressing them together to thermally bond the toner film on the recording medium. Japanese Patent Application Laid-open No. 2006-195429 also discloses a method including processes of forming a toner film by heating and pressing a toner film carried on a transfer and fixing belt, overlapping a recording medium with the toner film in which a bond layer has been formed by applying solvent, and pressing together to physically bond the toner film on the recording medium.
By the way, it is demanded lately to be able to form an image on a recording medium such as a recycled sheet, a thick sheet and an embossed sheet whose superficial ruggedness (roughness) is large. In case of the recording medium whose superficial ruggedness is large, the simultaneous transfer and fixing type image forming apparatus causes unevenness of density and lowers its image quality as described above. Meanwhile, Japanese Patent Application Laid-open Nos. 2001-272866 and 2006-195429 also have a possibility that the toner film does not fully adhere down to bottoms of concavities and separate from the recording medium, thus dropping strength of the image. There is also a possibility that the toner film cracks everywhere on the surface of the recording medium where there exist concavities and the image quality drops as well if the toner film is tried to be adhered down to the bottoms of the concavities from an aspect of intensity of the image.